Mini-Boss
by Reawakened Clam
Summary: Gokudera leaves them alone for barely a week and comes back to a chibified Tenth.
1. Hayato - Prologue

Gokudera nearly dropped his report when he entered the Tenth's office.

Now, being the faithful, respectable Storm Guardian and right-hand man of _the Vongola Decimo,_ standing in the doorway and staring stupidly at his boss would be considered inappropriate.

However finding a familiar looking 4 year old at the desk where a 24 year old should've been made him stop dead in his stracks. The fluffy, gravity-defying brown hair, light brown eyes, too-innocent-for-the-mafia look, heck the kid was wearing a freaking suit and was doing paperwork like it was nothing! Well, aside from the occasional grimace and rubbing of the head as he tried reading Italian.

 _Something must've happened to Tenth._

The kid looked up at the sound of the door opening, face brightenig into a way too familiar smile, and with a voice that had _no buisness_ being in a 4 year old body, "Ah, Hayato, you're back!"

 _What the fu_ \- "Language, Hayato." Tenth's voice rang in his head- ... _fudge._

A few moments of awkward silence passed as the Mini-Tenth looked at him expectantly. Was he supposed to say something?

Gokudera coughed a little, trying to break the silence. "Erm, Tenth...?"

Mini-Tenth nodded, smile brightening a bit at being adressed. _Oh my gosh is that seriously the Tenth?!_ "Is there something you need...?"

Gokudera blinked at the tiny form in front of him. He was... small. Very, very small, but something in his head screamed at him that ' _He's just really short_.' and immediately mentally kicked himself for thinking something as _utterly disrespectful_ as that. Mini-Tenth's smile faded a little as his large, emotional eyes narrowed slightly when he noticed he was getting stared at.

 _Agh! It must be something sensitive! I'm so sorry Tenth!_ Gokudera tensed slightly at the look Mini-Tenth was giving him, letting his gaze fall from Mini-Tenth to the floor rather awkwardly. He walked over to the desk and put his report down next to the paperwork piling up- _Holy mother of rainbows and sunshine he's_ way _smaller up close_. "Ah, no... Here's my report for the mission..." Mini-Tenth beamed with the power of a million kittens, puppies, bunnies, and all things cute. It was _blinding_. "Thanks, Hayato! Go get checked out by Brother, he should be with Lambo in the imfirmary, then you should rest up for a few days."

Gokudera got the feeling he didn't want to ask why they were in the infirmary. He merely nodded and with a quiet grunt, bowed slightly and walked out of the Tenth's office.

One the door closed behind him, all he could do was stare at the wall.

That four year old greeted him just like how the Tenth would. That four year old told him to go to Turf-Top after a mission just like how the Tenth would. That four year old smiled and told him to rest up for a few days with a knowing look just like how the Tenth would. That four year old _sounded_ just like the Tenth and even _looked_ like him...

 _Was that four year old seriously the Tenth?_

 _No, no that's ridiculous. The Tenth's a grown man, not a kid!_

 _You're in Vongola, anything is possible._

 _...Point taken._

As Gokudera stared off into space having an internal war over the kid's identity, he didn't notice Yamamoto walk around the corner. The Rain spotted him and where he was, eyes widening in horror, and rushed over to the Storm. The sword user quickly snapped his fingers in front of Gokudera's face, looking for some kind or reaction.

Gokudera jumped at the sudden noise, snapping his stormy green eyes onto amber brown. " _WHAT_ -?!"

A hand instantly clamed over his mouth, as Yamamoto grabbed his arm and dragged him away from the Tenth's office door. Gokudera clawed the taller man's hand from his mouth as soon as they started to slow down after making their way to the infirmary.

"What the hell, Sword Freak?!"

Yamamoto stopped, letting go of the now very irritated bomber. He fixed his gaze on him, dead serious. " _Please_ tell me you didn't mention his size."

Gokudera blinked, raising an eyebrow. "...You mean the Tenth?" At Yamamoto's affirmitive nod, Gokudera shook his head. "No... He gave me a look that suggested it was sensitive when I stared for too long..."

Yamamoto sighed in releif. "Oh thank goodness, he already put Lambo and Ryohei in the infirmary a few days ago when it happened."

"He _what_?" Yamamoto sighed, turning to look down the hallway where the infirmary was.

"Well it's not really _that_ bad-"

"What happened to the Tenth? Why does he look like a four year old?" Gokudera jumped in, not really wanting to hear about the Lightning and Sun. If they've been in there for days he doesn't think he'd want to know.

Yamamoto paused, pursing his lips. "Well about four days ago, two days after you left..."

 **~Four Days Ago~**

After the Arcobaleno were freed from the curse, and after Tsuna managed to get over having to deal with a six foot Reborn, Verde had taken to researching the Curse, or more importantly, the deaging part. Nobody was really sure why, but they didn't question it.

At some point Verde had visited the Vongola mansion to borrow the Ten Year Bazooka, claiming he could use it to aid in his research.

Lambo had thought that was a terrible idea, because anything Ten Year Bazooka related can't be good, and tried taking the purple time travelling machine back.

Let's just say Tsuna showed up at the wrong place at the wrong time.

After a bit of tampering with the Bazooka from Verde, it's affects were rather odd, reminding Tsuna and a few people who were present at the time of when five year old Lambo broke the Bazooka and only the bodies swapped.

After the rather ungraceful switch in the middle of pure chaos and destruction, Tsuna in all his four year old glory gave everyone a glare (more like pout in that body) and told them to "Shut up and just _let him take the damn Bazooka_."

He could only hope actual four year old Tsuna wasn't having too hard of a time in a 24 year old body.

Verde was given permission to use the Bazooka to try finding a cure for whatever happened since it was well over five minutes since the switch, and Verde had agreed, so long as he could use Tsuna as a test subject.

Unfortunately for everyone involved a bit of Tsuna's four year old self affected his twenty-four year old mind, and he made it _very clear_ he wasn't some guinea pig.

After several of the staff got sent to the infirmary, everyone agreed to just not mention his size lest they envoke his mini-tantrums once more.

 **~Back to the Present~**

Gokudera gave Yamamoto a long, hard stare. "You're telling me a bunch of trained mafiosi gone done in by a _four year old_."

"Well technically twenty-four-"

"In a four year old body." The bomber corrected. Yamamoto snapped his mouth shut, but gave Gokudera a serious look as if trying to say ' _You have no idea and I envy you for that_.'

Gokudera decided he _definitely_ didn't want to know how.

The silver haired man ran a hand down his face tiredly. This was _not_ what he needed after a long, exhausting trip. "So now we're stuck with a four year old running Vongola?"

Yamamoto nodded, "Pretty much."

Gokudera breifly wondered if he got a concussion on his trip and was just dreaming. "An adult in a child's body..." He mused quietly to himself. "That's a _dangerous combination_."

 **~Reborn!~**

 **A/N: So basically Tsuna got chibified (or Arcobaleno-fied without being an actual Arcobaleno) and is not happy. This'll likely be a series of connected one-shots that'll go on for who knows how long. I know they're probably a bit OOC, but these guys are the versions who had all the Future crap with Byakuran to put up with, so they grew up a bit differently in comparison with the TYL versions we saw in the Future Arc. I'm open to any ideas for what happens so go ahead and tell me in the reviews.**


	2. Tsuna - Lessons

If there was one thing Tsuna liked about himself, if anything at all, was the fact he had somehow managed to grow to 5'5. He had always been short, which annoyed him to no end when he was in middle school and almost everybody he met towered over him.

It wasn't much, but it was something.

And then that stupid, _stupid_ accident took out not only a good chunk of the mansion, but also a solid four feet of his height. That fact almost made him want to cry as badly as the mountains of paperwork flooding into his office because of it.

Just to let you know, being ankle height with everything and being unable to reach his precious coffee in the kitchen with tiny, stubby little hands, was not fun. He couldn't even go into HDWM with this tiny body!

Tsuna growled in frustration, staring up at the countertop where that god-given pot of beautiful coffee sat, impossibly high up and staring down mockingly at his new form.

When he was younger he couldn't stomach the bitter liquid, but after being forced through complete _hell_ these past few years with complete idiots as friends (no offence to them but _come on_ ) he had come to practically worship the life-giving beverage. He still got the ocassional stomach ache but it was _so_ worth it.

But now he couldn't even get to it. How on earth did Reborn survive this? Being so- so _tiny_?!

Of course, he's Reborn, the Strongest _frickin_ Hitman in the World (yes the capitalization is nessesary).

He gritted his teeth, eyeing the side of the countertop. If he could jump high enough to reach the handle bar on the drawer, then he could hoist himself up to get to his precious coffee.

Of course, he could just ask one of his friends or someone to just get his coffee for him, but NO! If he, the _Vongola Decimo_ , could get his coffee before, something like being stuck in a four year old body shouldn't hinder him from obtaining his heavenly drink!

With that plan in mind, he hopped in place for a moment, checking his jumping height. _Okay, I might make it, somehow!_

He stopped his hops, bending his knees and keeping his eyes on the prize. I can do this!

With that he leapt up, tiny hand reached out ahead of him ready to latch onto the handle and get up to the last thing _keeping him alive_ -

He smacked into the side of the counter, sliding down and landing harshly on his butt.

"Ow!" Tsuna yelped, scooting back a bit as he rubbed his sore spot. He took a moment to regain what little dignity he had left and stared back up at his coffee.

It just sat there, undisturbed as if smugly showing off how much higher it was than he was.

Tsuna's little fingers curled into a tight fist. He wasn't going down that easy! He swore to himself that he would not return to that hell full of paperwork emptyhanded!

The _Boss_ of the _Vongola Famiglia_ soon found himself trying to drag a chair over to the countertop, to no avail. He kept slipping and falling on his butt, failing to move a chair well over three times his size more than a few inches.

When he couldnt get it to budge any further, he stopped, gazing back over at the kitchen counter longingly. _My... My coffee..._

He wanted to cry in frustration. He just wanted coffee, is that too much to ask? His eyes were welling up with tears, much to his ever increasing frustration because _NO! I'M TWENTY-FOUR I SHOULDN'T CRY OVER SOMETHING LIKE THIS!_

Tsuna glared at the counter. _No_. No he _can't_ give up here. The counter was _mocking_ him and his new form. His pride was not going to take that sitting down _dang it_!

The toddler - _no I'm a grown man!_ \- found himself gripping a makeshift grappling hook made from whatever he could find lying around. (There were a surprising amount of socks and jewlry strewn about, he'll have to talk to the servants about those.)

His little grappling hook, comprised of several shoelaces and small ropes alongside some random wires, was far from pretty or even safe but he needed his coffee, alright? Anything'll do, besides, it's not like anyone's watching.

He readied his arm, swinging the hook and gaining speed. If he could just get it hooked around the handle he could climb up! _Come on come on come on_!

Tsuna let go, letting it go flying. _So close come on!_

It didn't land, bouncing off the side and smacking him in the head. Tsuna rubbed his forehead, eye twitching in annoyance. One more!

It took him a few more tries, each failed attempt followed by every curse under the sun in as many languages Tsuna knew. Or rather, every language Hayato knew, and Tsuna just picked up all the lovely explicit words to fall from the bomber's mouth, much to the Storm Guardian's horror.

Eventually, by some miracle, Tsuna finally managed to get the hook to land nicely on the handle, hooking onto it and staying firmly in place. The brunet have his rope-shoelace-wire contraption a tug, finding that it didn't budge, stable enough to keep him up.

 _Perfect_.

He pressed a foot against the side of the counter, tightening his grip on the likely-not-very-safe grappling hook, and started to climb.

Up. Up. Up.

 _Towards his sacred coffee._

It went well, at least, for a moment. He felt the rope jerk slightly, making him pause and noticed the strings coming undone.

 _Oh no no no no no not now!_ Tsuna tensed, panic bubbling in his gut as he started to move faster. He was only halfway up _no don't break please my COFFEE-!_

It snapped.

He found himself on the floor, rubbing his butt in pain again as he glared. _Not yet, I'm not done yet! I NEED MY COFFEE!_

The brunet got back up, scowling at the broken grappling hook. He could try a few other things to get up there, but his headache was already getting worse from all this. Half an hour, and still no coffee. He couldn't take this much longer.

With a final huff, Tsuna took a few steps back, before realizing he only went back about two feet, and took a few more until he had a nice running distace between him and the countertop, where that beautifully hot coffee machine awaited him.

If Reborn could do it, so could he... maybe not as well but come on he could still _try_ dang it.

With that in mind, the twenty-four year old sucked in a breath, braced himself, and ran- well, as best he could when he was stuck in a tiny four year old body.

It felt like miles upon miles he ran, and when he finally got close enough, he steeled his chubby little legs and _jumped_.

 _So close so close yes yes come to me COFFEE-!_

Stupidly giant hands suddenly grabbed at him midair, and Tsuna bit down a shriek, wailing inside as he was pulled away from his precious coffee. He was turned around to face Takeshi- _oh sweet sweet Takeshi please give me my coffee_ \- who blinked at him with an oblivious smile.

"Yo, Tsuna! Whatcha think you're doing?"

Tsuna twisted in the raven head's grasp, peeking over his shoulder at his goal desperately. "Trying to get coffee...?"

Takeshi laughed, shaking his head and he started walking towards the fridge, _still holding Tsuna_. "Now now, you wont be able to stomach it in that body, c'mon have some milk!"

 _Damn it, nevermind, he's dead to me_. Tsuna let out a low growl, thankful his adult voice had been preserved. Nobody would take him seriously if it changed with his body. The combination may have looked really weird but he didn't care at this point. "Takeshi, wait! I really _really_ need my coffee right now-"

Takeshi didn't seem to hear him, happily opening up the fridge and taking out a carton of milk.

Oh _hell_ no.

Tsuna twisted in Takeshi's grasp, kicking as hard as he could and- _wait why aren't any of my hits landing?_

Tsuna flailed helplesslly, legs too _short_ to hit anything and clawing at the man's arm trying to squirm his way out. Takeshi- _no,_ Yamamoto _, he's_ so _dead to me_ \- sat him down on a pile of books stacked on top of a chair and slid him a glass of milk.

 _Milk_.

Tsuna just wanted his coffee.

"You couldn't have coffee when we were in middle school, if I remember right," Yamamoto mused, seeming oblivious to Tsuna's boiling frustration. "So I don't think you'll be able to handle it at four- eh?"

Finally, finally he turned and noticed Tsuna sending him the most threatening death glare he could. Yamamoto froze, blinking owlishly at him, smile slipping.

 _Yes. Fear me. Give me my coffee._

They stared at each other for a minute, completely silent. Yamamoto slowly reached forward...

...and patted him on his head.

Tsuna stared at his Rain Guardian in disbelief as the man laughed, in his face, at his death glare!

"Aww, you're so cute when you're angry!"

 _NO! DON'T YOU DARE CALL ME CUTE! FEAR ME DAMN IT!_

Tsuna's growls and glares only seemed to make Yamamoto laugh louder, _cooing_ of all things at him being _cute_ and _adorable_.

This wasn't how it was supposed to go. He was supposed to get his coffee. His increasing headache demanded it.

"Ta- _Yamamoto_ stop!" Tsuna swatted the man's hands away, pointing at the coffee machine. "I want _that_."

Yamamoto glanced up at the machine, quirking a brow. "But you can't drink that."

"Yes I can."

"No you can't."

"Yes. I. _Can_."

"No. You. _Can't_."

"YES I CAN!"

"Nah, Tsuna," Yamamoto nudged the glass of milk closer. "C'mon, you have milk right here, try it!"

Tsuna crossed his arms, glaring at the glass (he ignored the Rain's aww-ing). "Coffee."

"Milk."

"Coffee."

"Milk."

" _Coffee_."

" _Milk_."

"Fine I'll drink the milk _but_ only if you let me have my coffee first!"

Yamamoto laughed lightheartedly. "Okay but just a little! Can't have my boss getting an upset tummy!"

Did he just say _tummy_?

Tsuna watched at Yamamoto walked back over, fixing up a cup of coffee- wait are those the little mugs Reborn used to use? Tsuna didn't know if he should be grateful or annoyed.

When Yamamoto came back, the brunet was quick to snatch up his precious coffee, blowing on it a bit before drinking some.

There was no way he couldn't have coffee, he's still twenty-four! _Yamamoto's totally wrong!_

...o0o...

 _Yamamoto was totally right._

Tsuna sipped his glass of milk in frustration, rubbing his sore stomach as Yama- _Takeshi_ gave him a knowing look. "Don't look so gloomy, Tsuna! Besides, if it's your four year old body from the past, maybe drinking a lot of milk now will help you grow!"

Tsuna froze, staring at Takeshi.

That's... that's _right_. Milk is supposed to help your bones grow strong, right? He also remembered Takeshi drinking lots of milk when they were kids and he was a giant even back then! So- so does that mean if he drank a lot of this stuff while in his four year old body he'll grow _taller_?!

With that in mind, Tsuna quickly got back to drinking- now chugging- his milk, much to Takeshi's amusement. He finished up within seconds, slamming the glass down and looking up at Takeshi, a determined glint in his eye. "Gimmie another one."

Takeshi seemed to try choking down another laugh as he got up to refill the Decimo's glass of milk.

It took him far too long to notice he had a mostache of milk on his face.

It also took him far too long to notice his glares looked more like pouts in this body, much to his despair.

...o0o...

 **A/N: I- I don't even know. I recall on the wiki it says Tsuna can't have coffee, so, yeah. Sorry this took like, almost a year to update, dang. No I'm not gonna abandon this or anything, but don't expect regular updates. Those will pop by randomly lol.**

 **Also thanks to assassin8 for checking this over! It's cause of her this thing is longer than I intended LOL**

 **Thanks for reading! I'd love you hear your thoughts in the reviews, and I'm completely open to ideas by the way!**


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